As a recently established tenure track investigator at the NCI, only very preliminary ideas in this project can be presented. We plan to perform chemical screenings to identify compounds able to induce quiescence in pluripotent cells such as mouse embryonic stem cells. For this we envision the generation and use of three different cell line reporters: 1) A pluripotent cell line expressing a fluorescently-labelled p27-mutant form unable to interact with CDKs and only stable in quiescent cells. 2) A pluripotent cell line expressing a fluorescent reporter protein that shuttles between the nucleus and the cytoplasm based on CDK activity. 3) A pluripotent cell line with an endogenous reporter for a gene highly expressed in diapaused embryos.